The use of electronic devices by investigators to track Scott Peterson's movements was an unorthodox move, observers said Thursday.
Prosecutors intend to introduce evidence from a global positioning system tracking device, Senior Deputy District Attorney Rick Distaso said at a hearing this week.
Defense attorney Mark Geragos countered that he would seek to have the evidence excluded, indicating that there were problems with the GPS equipment.
The issue is likely to be hashed out at an Oct. 20 hearing to determine whether there is enough evidence to put Peterson on trial on charges of murdering his pregnant wife, Laci, and the couple's unborn son, Conner.
Authorities used "wiretaps on phones, tracking vehicles, all of the technology available" as they probed Peterson's death, state Attorney General Bill Lockyer said at a news conference April 18 the day that her husband was arrested in La Jolla.
Peterson, 30, could receive the death penalty if convicted of both murder counts.
His wife was almost eight months pregnant when she was reported missing Christmas Eve. Her body and that of her son were found in mid-April along the eastern shore of San Francisco Bay, several miles from where her husband said he went fishing Dec. 24.
During a four-month probe, investigators employed a range of tactics, including "hypnosis techniques" on a witness.
Police also attached a tracking device to Peterson's pickup, Lockyer said at the April news conference.
Such tracking equipment usually is employed by state and federal law enforcement in major drug cases, according to experts.
"The fact that they used one in this case shows law enforcement were being very resourceful," said James Hammer, San Francisco assistant district attorney. "They were doing things that are not particularly done in a homicide case."
Most police and sheriff's departments do not have the budgets for tracking equipment, Sacramento County Sheriff's Department spokeswoman Sharon Chow said.
"That's out of our league," Chow said. "Tracking devices for vehicles are very expensive."
It is unclear what evidence the tracking devices produced. Authorities and the defense have successfully sealed most documents in the case, and Judge Al Girolami has imposed a gag order preventing the parties from talking about evidence.
Tracking devices could serve the prosecution if they show that Peterson returned to the bay, tie him to a location where physical evidence was found or indicate that he was preparing to flee the country, Hammer said.
"If he's going back to the bay to make sure nothing floated up, that he didn't leave anything behind, that would help a prosecution theory," Hammer said.
But prosecutors will have to demonstrate that the tracking evidence is relevant to the case and that the equipment worked properly, some observers said.
"If he went to Mexico, so what? He came back," veteran Los Angeles criminal defense attorney Bradley Brunon said.
"If it's somewhere incriminatory, you try to get it excluded," Brunon said. "Incriminatory evidence that's accurate is damaging enough. If it's inaccurate, you certainly want to object."
GPS equipment uses a network of Defense Department satellites to identify positions on Earth. Most single receiver equipment, usually used in tracking devices, has an accuracy of 30 to 300 feet, said Kenneth Foote, geography department chairman at the University of Colorado at Boulder.
"That kind of tracking, where they are following people's paths along highways, GPS is very good for that," Foote said.
But using it to determine a person's exact location is more problematic.
"Sometimes the settings are not put in correctly, and it may be reading coordinates wrong," Foote said. "They're subject to the same human error as setting up a VCR."
The tracking device that Lockyer referred to appears to have been placed in the Dodge Dakota pickup that Peterson purchased after police used a search warrant in December to seize his Ford F-150 truck.
Police used another search warrant in February to take the Dodge, but returned it several hours later.
Court documents show that police obtained search warrants for three other unspecified vehicles used by Peterson. He was seen driving three other vehicles after the seizure of his Ford pickup.
At least one of those vehicles was a rental car registered to Enterprise Rent-A-Car, records show.
Christy Conrad, an assistant vice president of public relations for Enterprise, would not comment on how many vehicles Peterson rented from the com- pany or whether police placed tracking devices in them.
Bee staff writer John Coté can be reached at 578-2394 or firstname.lastname@example.org.